A therapeutic method called apheresis therapy in which blood of a patient is temporarily taken out of the body, etiologic substances in the taken-out blood are removed by a process such as adsorption or filtration, and the blood is then returned into the patient's body is known. That apheresis therapy is utilized in therapy for drug intoxication, food intoxication, and familial hypercholesterolemia, therapy for autoimmune diseases such as ulcerative colitis, Crohn's disease, articular rheumatism and the like, and is used to remove from the blood of a patient substances such as drugs, toxins and cholesterol, and inflammatory cells such as white blood corpuscles and blood platelets, which are considered to be causes of the diseases indicated above.
As apheresis therapies as indicated above, a double membrane filtration plasma exchange therapy (DFPP: Double Filtration Plasmapheresis) in which plasma is separated from blood by using a primary membrane and then the plasma is passed through a secondary membrane, and a direct blood perfusion therapy (DHP: Direct Hemo Perfusion) in which a body fluid of a patient is directly processed are known. The DHP, whose process is simple and convenient, is rapidly spreading in recent years. As for the form in which the column for use in the DHP is used, there exists, besides the form in which the column is used singly, a form in which in dialysis performed on a patient with renal failure or the like, the column is used by linking it in series to an artificial kidney, whereby β2-microglobulin, which is a causative substance for dialysis-related amyloidosis, which is a dialysis complication, and the like can be efficiently adsorbed.
In the DHP as described above, blood is passed through a column within which an adsorbent is housed, and removal-object substances in the blood are adsorbed to and removed by the adsorbent. A column as indicated above usually has a hollow cylindrical casing at whose two ends in a lengthwise direction there are disposed header caps provided with an inflow opening or an outflow opening for blood. An adsorbent is housed inside this casing. By disposing filters having many small openings at an end portion of the casing via which blood flows in and an end portion via which blood flows out, it becomes possible to hold the adsorbent within the casing.
Generally, when a blood purification column is used as a medical instrument in the DHP or the like, a so-called priming operation in which the column, before being used, is subjected to the passage of and the filling with physiological saline or the like. At this time, if air occurs in the column or the circuit and resides in the column, the air impedes the passage of and the filling with physiological saline or the like and the contact areas between the adsorbent and blood is reduced so that a decline in the adsorption-removal performance of the blood purification column is sometimes brought about. Furthermore, in a column in which a filter disposed at an end portion of the column is poor in air removal, that is, a column that has a filter through which when air is once taken into the column the air is not easily removed to the outside of the column, blood in the column is likely to be activated to coagulate due to air that remains in the column. In particular, in a column used in a form in which the column connects in series to an artificial kidney as stated above, the washing (priming) of the column and the artificial kidney performed prior to the therapy is preferred to be performed in a state where the column and the artificial kidney connect in series from the viewpoint of operability. However, when as the artificial kidney, an artificial kidney in a moist state or a dry state and not filled with water is used, a large amount of air flows into the column. Therefore, as for the filter for use in the column, a property excellent in air removal and, at the same time, excellent in biocompatibility, that is, that is unlikely to induce in-circuit coagulation or the like at the time of blood circulation, is required. Up to the present, patents that indicate that a mesh is used for fixation of an end portion of a column for use in the DHP have existed (Japanese Unexamined Patent Publication (Kokai) No. 59-95051 and Japanese Unexamined Patent Publication (Kokai) No. 2009-254695). However, as for a mesh, there is only a description that a mesh designed to be capable of retaining an adsorbent within a column should be used, and there is no description about bettering the aforementioned air removal characteristic by a design of a mesh. Furthermore, there is also an invention in which meshes are provided at two ends of a column that, as an adsorbent within the column, uses an adsorbent made up of fiber in a hollow yarn state or a solid yarn state (Japanese Unexamined Patent Publication (Kokai) No. 2010-148851). However, that invention, too, does not discuss air removal. On the contrary, the meshes are created by rolling the adsorbent with a web-state cloth for the purpose of stably retaining the in-column adsorbent or improving the in-column flow. Disposing such a mesh that is open parallel with the column longer-axis direction is not preferable from the viewpoint of air removal characteristic.
It could therefore be helpful to provide a filter contained in a blood purification column and improve the removal characteristic regarding air that gets into the column and to prevent blood activation due to air remaining in the column and decreased adsorption performance due to a decrease in the contact area between blood and an adsorbent.